Lore (stylized as LORE or L O R E) is a meme on the SiIvaGunner channel, especially within the channel's community. It referenced in the question "Is this LORE?", which is asked sarcastically about anything that seems abnormal, not just actual "lore".
The word "lore" refers to the information about traditions, knowledge, and customs about a certain group. Many different fanbases, such as Star Wars and Lord of the Rings, study and theorize about the "lore" to uncover the often obscure (and ridiculous) background of their obsessions. "Lore" is also used as a synonym of "story".
On SiIvaGunner Edit
As a bait-and-switch channel, SiIvaGunner did not have its own story until the Reboot arc. When the Reboot arc happened, fans of the channel were swamped with questions, especially about the Alternate Reality Game (ARG) that occurred with the "album" -. Many people were (and still are) confused about the story of SiIvaGunner, and so the YouTube comments were flooded by "Is this lore?".
"Is this lore?" is still used sarcastically on the channel to describe unusual rips, such as shitposts and meme-filled videos.